april 20th is a long mythical [since 1971 at least] day of celebration for marijuana smokers. Anil, thanks for the explanation of the circuit, i was unaware of currents affect on human heart was so low.

Probably late answer but if somebody is searching like I was :)
One of the solution is to use HC-SR04+ version (support 3.3v)
I have tested it on my Omega2+ and it works fine. Or if you already have 5v version just use resistors (plenty examples on net). I played little bit with c++ using Patryk27 Omega2-GPIO library. You can check my code and compiled app at github:. I'm still playing with this script.

I bought SDS021 and would like to extend it's life. As per product sheet this sensor can be putted into sleep mode. Sleep mode can extend life of this sensor. According to vendor information SDS021 laser will last up to 8000hrs (~1 year) of continious work.
Do you know how to put SDS021 into sleep mode via python and wake? I do not need to have air quality delivered every second. Would like to start script from cron hourly.

@MultiDJRoni While the display you reference (http://ebay.eu/2brESNp or http://ebay.eu/2bYf3pA) communicates via I2C and is potentially controllable from the Omega, I don't know whether or not the chip/display it uses is the same as or compatible with that used in the OLED expansion. If it is not, you may be up for additional coding work to control it from the Omega (not a totally trivial task).

I still think you would be better of using a Prototype Expansion (http://www.robotshop.com/en/proto-expansion-for-onion-omega.html) between your Expansion Dock and OLED Expansion and wiring the Prototype Expansion to provide access to the I2C lines (GPIO 20, GPIO 21, 5v, Gnd) and other pins you need for access to your other devices.

@Ian-Pun
That is a great example to work from. Thank you.
Only problem I have now is trying to convert the temp into F.
I have tried adding the calculations in everywhere I can think of and I just get errors.
Any help would be great. I am real new to python programing.